The invention concerns a grinding arrangement with a grinding stone for the grinding of a knife.
On harvesting machines and harvest preparation machines such as, for example, a forage harvester, knives are employed for chopping of plant material and other materials. These knives become dull when so employed and must be ground. In the state of the art, various manual and automatic grinding mechanisms are known.
In the known grinding mechanisms, grinding stones of the most diverse shapes and materials are employed. As a rule, the grinding stone is fastened to a grinding stone retainer and is moved over the width of the knives during the grinding process and successively fed towards the knives. In addition to the knives that are being sharpened, the grinding stone also wears during the grinding process. It is therefore possible for the grinding stone retainer to come into contact with the knives that are to be sharpened when the grinding stone is completely worn and thereby damages the knives.
The problem underlying the invention is seen in the aforementioned disadvantages in the state of the art.
According to the invention, there is provided a novel way of preventing damage to the cutting knives of a forage harvester coming into contact with a grinding stone retainer, during the sharpening process, after the grinding stone is worn away.
A broad object of the invention is to preventing possible damage to the knives by the grinding arrangement by constructing a grinding stone such that its worn condition can be easily detected so that a worn stone can be replaced promptly by a new one.
A more specific object of the invention is to provide a knife grinding stone and detection arrangement constructed for use with each other so that an electrical signal is transmitted when the wear limit of the grinding stone is reached, the signal being used for the control of an indicator arrangement that informs the user of the need to replace the grinding stone.
A alternative or additional object of the invention is to provide knife grinding stone and detection arrangement wherein the detection arrangement may also control the grinding arrangement in such a way that grinding is possible only with a grinding stone that has not yet reached its wear limit.
Yet another object of the invention is to provide a further alternate construction wherein the indicator arrangement is loaded with another message that warns the user shortly before reaching the wear limit that the grinding stone must soon be replaced, this being performed by a detection arrangement that senses a second wear condition of the grinding stone, that lies just ahead of the wear limit.
Another more specific object of the invention is to provide a grinding stone arrangement including a conductive element embedded into the grinding stone that is, in one case, destroyed upon reaching the wear limit, and in another case, becomes exposed, with the detection arrangement being constructed in accordance with the particular case to sense the condition of this element. The detection arrangement may include a microprocessor that forms a component of the control arrangement of the grinding and/or cutting arrangement.
A further alternative or additional object of the invention is to provide an optical sensor whose output signal changes as soon as the wear limit of the grinding stone is reached. For this purpose, for example, an optical sensor is located at a cavity provided in the grinding stone into which ambient light falls upon reaching the wear limit, this light being sensed by the optical sensor.
These and other objects of the invention will become apparent from a reading of the ensuing description together with the appended drawings.